The compound of the structure
(or its hydrochloride salt, or trifluoroacetic acid salt) (hereinafter the above DPP4-inhibitor or saxagliptin) is an orally active reversible dipeptidyl peptidase-4 (DPP4) inhibitor, which is a therapeutic agent for treatment of Type-2 diabetes mellitus, obesity and related diseases which is disclosed in U.S. Pat. No. 6,395,767, Example 60.
U.S. application Ser. No. 10/716,012 (Publication No. US2005/0090539A1, published Apr. 28, 2005) discloses a process for preparing saxagliptin including the benzoate salt thereof (Scheme VII, Example 41), the free base (Example 42), free base monohydrate thereof (Example 42) and the hydrochloric acid salt thereof (Scheme VIIB, Example 42), the disclosure of which is incorporated herein by reference.